package com.untils;

import java.util.Random;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class RandomUtil {
    private static final Random random = new Random();

    private static final DecimalFormat fourDf = new DecimalFormat("0000");

    private static final DecimalFormat sixDf = new DecimalFormat("000000");

    public static String getFourBitRandom() {
        return fourDf.format(random.nextInt(10000));
    }

    public static String getSixBitRandom() {
        return sixDf.format(random.nextInt(1000000));
    }

    /**
     * 给定数组 抽取n个数据
     */
    public static ArrayList getRandom(List list, int n) {
        Random random = new Random();

        HashMap<Object, Object> hashMap = new HashMap<Object, Object>();

        // 生成随机数字并存入HashMap
        for (int i = 0; i < list.size(); i++) {
            int number = random.nextInt(100) + 1;
            hashMap.put(number, i);
        }

        // 从HashMap导入数组
        Object[] robjs = hashMap.values().toArray();

        ArrayList r = new ArrayList();

        // 遍历数组打印数据
        for (int i = 0; i < n; i++) {
            r.add(list.get((int) robjs[i]));
            System.out.println(list.get((int) robjs[i]) + "\t");
        }
        System.out.println("\n");
        return r;
    }
}
